There is no magic button for this...
The only way to do it is to rebuild the Operating System on the disk - to do this you will need the OS Media CD.
When you rebuild the OS you will lose all data, applications and device drivers you have added over time.
You are obviously trying to resolve a problem of some sort - it may be a better approach to try to fix the problem that concerns you - you do not describe the trouble with the machine.
Sometimes just returning to a Restore Point (of a few days/weeks ago) will solve a problem.
Good luck...
Peccavi, August 2010
